Protective device



1949. G. F. LINCKS PROTECTIVE DEVICE Filed March 21, 1945 J \NORMAL LIQUID DIELECTRIC LEVEL Inventor: George F. Lincks,

by W Hi Attorney Patented Jan. 11, 1949 PROTECTIVE DEYICE George F. Linoks, Pittoiield, Man auignor to General Electric Company, a corporation of C New York Application March 21, 1945, Serial No. 533,900

My invention relates to a protective device, and more particularly to a fuse protective device for .protecting electrical apparatus such as transformers and the like which may be of the liquid insulation-filled type. Specifically my invention is an improvement on United States Letters Patent 2,337,853, Smithygranted December 21, 1943, and assigned to the same assignee as the present application.

Electrical devices, such as distribution transformers and the like, often have fuses or the like mounted within the transformer itself. When these fuses were mounted in the transformer it was necessary to employ fusible elements, sometimes called weak links," having relatively high ratings to insure against their rupturing or blowing except in the case of an internal fault in the electrical device. In such a case it was necessary to recondition the transformer so if the fusible elements only blew under such conditions there would be no objection to taking the transformer to a service shop to replace the fuse since it must be taken to the service shop anyway. However,

service experience has shown it necessary to use lower rated fuse links so that there willbe sufficient current to cause the fusible element to melt when the electrical device is located out toward the end of long lines, and also so as properly to sectionalize the primary lines to maintain the desired continuity of service. fuses with sufficiently low ratings to meet these requirements it is not only desirable but imperative to be able to renew or replace these fuses in thefleld without sending the transformer back to a shop or factory.

It is an object of my invention to provide a new and improved renewable bushing fuse of the expulsion type. V

It is another object of my invention to provide a renewable bushing fuse of the expulsion type with means for elongating the arc in the liquid dielectric 'so as quickly to interrupt the circuit.

It is another object of my invention to provide a bushing fuse which may readily be replaced in the field which is simple and compact and inexpensive to manufacture.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to the accompanying draw- 3 Claims. (01. zoo-13s) ing in which Fig. 1 is a sectional view of the bushing of a transformer illustrating the fused protective device of my invention; Fig. 2 is an enlarged view of a resilient member which forms the lowercontact to which the bushing fuse is connected; Fig. 3 is a perspective view of a locking device employed with my invention; Fig. 4 is a view partly in section of the lower portionei the bushing of Fig. 1 illustrating the condition of the fuse device upon operation thereof, and Fig. 5 is a sectional view of the portion of the bushing illustrated in Fig. 4 showing a modification of my invention.

Although my invention may be employed in the protection of electrical apparatus other than transformers, I have elected for the purpose of describing and illustrating my invention to show it as applied to the protection of an electric translating apparatus such as a transformer.

Referring now to the drawing, I indicates the casing of an electric translating apparatus, such In order to employ as a transformer, which may contain the usual windings and insulating liquid dielectric.

thereto. Supported on cover 2 and extending from the top thereof is at least one insulated high voltage bushing I through which electrical connections with the high voltage windings of the transformer may be made. The bushing 3, preferably formed of porcelain or the like, is provided with an axially extending passageway or chamber 4 through which the high voltage lead extends so that connections may be made with an external electrical circuit. The bushing I, preferably constructed of a ceramic insulating material, includes a depending portion 5 which extends for some distance beneath the cover 2 of easing I and in fact,'as indicated in Fig. 1, extends below the normal level of the liquid dielectric contained in casing I.

The passageway or chamber 4 within bushing 3 is substantially of uniform cross section except for an annular recess 6 formed near the upper or external portion of the bushing, the purpose of which will become apparent as the following description proceeds. Also near the lower or internal end of bushing 3, there are provided a plurality of annular recesses l, the purpose of which will also become apparent from the following description.

In order to provide a readily removable or renewable bushing fuse, it is desirableto provide a lower contact in bushing I which may be removably connected with the fuse device to be Casing I may be provided with a ,cover 2 suitably fastened described hereinafter. Ihave illustrated a construction by way of example only and it will occurto those skilled in the art that the lower contact may be held in the bushing by any suitable means such as clamping, cementing, or the like. In the illustrated'construction this lower contact member, indicated at 8 in Fig. 1, comprises a resilient sheet of conducting material having the upper and lower ends thereof displaced at a slight angle indicated at 8 in Fig. 2 and with a plurality of prongs l cut from the upper edge thereof and deflected a somewhat greater amount, as indicated in Fig. 1. A plurality-of prongs integral with contact 8, similar to the prongs I0, are provided along the lower edge of contact 8, which aredeflected in the same direction as prongs ID, as is clearly shown in Fig. 1. An extension II to which an electrical conductor, such as l3 may be connected, is integrally formed with contact 8. Contact 8, which tends to be in the form of a sheet when free of bushing 3, is adapted to be rolled into cylindrical form and inserted into the lower or internal and of bushing 3 so that the prongs I0 and II spring into recesses 1 thereby holding lower contact 8 in position in bushing 3. By virtue of the deflected portionsil upper and lower diverging entrance portions to the cylindrical contact 8 are provided, enabling the terminal of the fuse device to be readily inserted therein and removed therefrom. The insulated conductor I3 is preferably permanently connected as by welding or soldering with extension l2. It will be understood that insulated conductor I3 is connected to the high voltage winding of the transformer or translating apparatus.

The fuse device of my invention may be very similar to the fuse device disclosed in the above mentioned Smith patent except that conductor l3 must be permanently fastened to contact 8 and thus cannot move away with a suitable end cap to elongate the arc in the liquid dielectric as was done by Smith. However, this is accomplished in a new and novel manner as hereinafter described. As illustrated, this fuse device comprises a tube M of insulating material. The lower end of fuse tube I4 is closed by a cap I5 provided with a vent l8 so that liquid dielectric may enter fuse tube I4. The lower end of fuse tube I4 is also provided with an annular terminal or contact ring I] which is electrically connected to cap l5 by a conductor l8 which is suitably covered with insulating material so the are that forms between the burned end of the fuse element 20 in the fuse tube l4 and the cap l5 cannot strike thereto when the cap I5 is blown from the end of the tube M as illustrated in Fig. 4. The conductor preferably has considerable length and is coiled about the lower end of the fuse tube as indicated at l9 so cap IE will continue to be electrically connected to contact ring ll when blown from the end of the fuse tube I4 and thus can elongate the arc in the liquid dielectric. Mounted within the lower end of fuse tube i4 is a fusible element 20 elecing the vent.

In order to seal the passageway at the ex- I ternal end of bushing 3 it is desirable to provide means for locking the fuse device comprising fuse tube l3 in passageway 4. To this end I provide resilient locking means comprising a washer 24 having a plurality of resilient prongs 23, best shown in Fig. 3. Washer 25 is adapted to be placed over threaded terminal 22 of the fuse device with the prongs extending in an upward direction. A terminal, and sealing member 28 for the transformer or electrical apparatus, having a female threaded portion 21, is adapted threadedly to engage terminal 22 whereupon prongs 35 of the locking washer 24 are spread into the annular recess 8 effectively locking the fuse device in passageway 4. Terminal 26 is also provided with a circumferential flange 23 adapted to cooperate with a sealing gasket 29 effectively to seal the upper end of passageway 4. While terminal 26 and flange 23 are shown as a unitary part they could be made as separate parts and arranged so that terminal 23 need not be turned in order to seal the upper passageway and thus the conductor which normally would be attached to terminal 26 need not be removed.

Upon rupture of the fusible element the expulsion action of the fuse device will cause cap l5 to blow on in the manner indicated in Fig. 4 so as effectively to interrupt the circuit by elongating the arc in the liquid dielectric since the arc must follow the cap l5 because the insulation on conductor l8 prevents it striking to conductor 53. By the construction hereinbefore described 3 the quick elongation of the arc is made practical and yet a new fuse device may readily be inserted in the field by merely unscrewing terminal and sealing member 28 whereupon the prongs 25 of trically connected to end cap I5 at one end therethe locking device 2 3 spring inwardly and the old fuse device may be removed and a new one inserted.

In Fig. 5 I have illustrated a modification of my invention in which a slightly different fuse device is employed comprising a fuse tube 30. Corresponding parts of Fig. fivare designated by the same reference numerals as in the preceding figures. Instead of fusible element 23 being connected electrically to cap 33 it extends through cap 33 around the end of the fuse tube and is connected to end 32 Of lower fuse terminal 3|. Lower fuse terminal 3| which engages contact 8 is spring biased so end 32 of terminal 3| will move away from fuse tube 30, to the dotted position indicated, when end cap 33 is blown free by the expulsive action of the fuse device. Lower fuse terminal 3| is restrained from movement by engagement with cap 33 at end 32 as illustrated in Fig. 5 so no strain from its biasing means which is preferably inherent in terminal 3| is exerted on fusible element 30. End cap 33, which is provided with avent 34 through which fusible element 20 extends, may be formed of any suitable insulating material, such as flber, so when it falls to the bottom of the transformer tank upon being blown from fuse tube 30 it will not detrimentally affect the future operation of the transformer. The are is elongated in the liquid dielectric quickly to interrupt the circuit by movement of end 32 of fuse terminal 3| after end cap 31 is blown off instead of by movement of end cap i5 at the end of flexible conductor H! as in Fig. 4. It willbe appreciated by one skilled in the art that end cap 33 in Fig. 5 could be omitted and end 32 of fuse terminal 3| could be releass,sss,ess

ably latched to the end of fuss tube fl or a strain wire could be used connected in parallel with fusible element fl 'so as to relieve the fusible. element II from the stress-of the bias which other- .wise might cause it to be damaged orstretched to the breaking point during normal operation.

From the above discussion it will be obvious that I have provided renewable bushing fuses which provide foreiongation of the. are in the liquid dielectric quickly to interrupt the circuit. which is readily replaceable in the field. and consequently may be more widely used since the curr'entrating thereof need not be so high as to be blown only in the event of an internal fault on the electrical apparatus.

While I have shown and described my invention in connection with certain specific embodiments, it should be understood that my invention is not limited to the specific details herein illustrated, and that changes and modifications may Occur to one skilled in the art without departing from the spirit and scope of my invention as set forth in the appended claims. 1

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an electrical device including a high voltage bushing. a passageway in said bushing, an annular recess in said bushing ad- Joining said passageway, a renewable bushing fuse having a terminal adapted to be inserted in said passageway, a locking member insertable in said passageway having an opening therein through which said terminal extends, and means adapted to threadedly engage said terminal for forcing said locking member into said recess to hold said fuse immovable in said passageway whereby the end of said passageway at the external end of said bushing may be sealed, said locking member'being resilient and positioned relative to said bushing fuse, passageway and recess for release therefrom upon disengagement of said means from said terminal.

2. In combination with an electrical device including a high voltage bushing, a passageway in said bushing. an annular recess in said bushing adioiningsaid passageway near the external end of said bushing, a renewable bushing fuse having a terminal adapte'dto be inserted in said passageway, a washer with prongs insertable in said passageway so that said terminal extends therethrough. and means adapted to threadly engage said terminal for forcing said prongs into said recess to hold said fuse immovable in said passageway and for sealing the end of said passageway at the external end of said bushing, said prongs being resilient and positioned relative to said bushing fuse, passageway and recess for 1 release therefrom upon disengagement of said means from said terminal.

'3. A renewable bushing fuse device for electric apparatus of the type employing a liquid dielectric and including a high voltage bushing with a passageway for said fuse device in said bushing, comprising a fuse tube of insulating material, terminals mounted on said fuse tube, a fusible element in said fuse tube electrically interconnecting said terminals, a coacting terminal engageabie with one of said fuse tube terminals. locking means in said passagewayhaving resilient portions engageable with saidcoacting terminal upon movement thereof in one direction relative to the fuse terminal for rendering said bushing fuse immovable in said passageway and upon movement in the opposite direction to release said locking means for rendering the bushing fuse removable from said passageway, and sealing means apparatus of the type employing a liquid dielectric and including a high voltage bushing with a passageway for said fuse device in said bushing, comprising a fuse tube of insulating material, terminals mounted on said fuse tube, a fusible element in said fuse tube electrically interconnecting said terminals, a resilient contact supported within said passageway so as to be electrically connected with one of said terminals when said fuse device is in said passageway, a coacting terminal engageable with one of said fuse tube terminals, locking means in said passageway having resilient portions engageable with said coacting terminal upon movement thereof in one direction relative to the fuse terminal for rendering said bushing fuse immovable in said passageway and upon movement in the opposite direction to release said locking means for rendering the bushing fuse removable from said passageway, and sealing means around said coacting terminal for simultaneously sealing one end of said passageway when the terminal is moved in the direction to effect the locking action of said locking means. w

a 5. A renewable bushing fuse device for electric apparatus of the type employing a liquid dielectric and including a high voltage bushing with a passageway for said fuse device in said bushing,

comprising a fuse tube of insulating material, terminals mounted on said fuse tube. a fusible element in'said fuse tube electrically interconnecting said terminals, a coacting terminal engageable with one of said fuse tube terminals. locking means in said passageway having resilient portions engageable with said coacting terminal upon movement thereof in one direction relative to the fuse terminal for rendering said bushing fuse immovable either axially or radially in said passageway and upon movement in the opposite direction to release said locking means for rendering the bushing fuse removable from said passageway, and means coacting with said releasable locking means for simultaneously sealing one end of said passageway when the coacting terminal is moved in the direction to effect the locking action of said locking means.

6.,A renewable expulsion bushing fuse device for electric apparatus of the type employing a liquid dielectric and including a high voltage bushing with a passageway for said fuse device in said bushing, comprising a fuse tube of insulating material, an axial terminal mounted partially within and at one end of said fuse tube, a coaxial terminal mounted outside of and closely adjacent the opposite end of said fuse tube, a fusible element located in said fuse tube closely adjacent said opposite end and electrically interconnecting said terminals, means mounted adjacent said fusible element at said opposite end and renewable with said fuse device for quickly elongating the arc in the liquid dielectric when said fusible element is melted, a coacting terminal engageable with said axial terminal, locking means in said passagewayhaving resilient portions engageable with said coacting terminal upon auam electric and including a high voltage bushing with a passageway for said fuse device in said bushing, comprising a fuse tube of insulating material, an axial terminal mounted partially within and at one end of said fuse tube, a coaxial terminal mounted outside of and closely adjacent the opposite end of said fuse tube, a fusible element located in said fuse tube closely adjacent said opposite end and electrically interconnecting said terminals, a resilient contact supported within said passageway so as to be electrically connected with one of said terminals when said fuse device is in said passageway, a coacting terminal engageable with said axial terminal, looking means in said passageway having resilient portions engageable with said coacting terminal upon movement thereof in one direction relative to the axial terminal for rendering said bushing fuse immovable in said passageway and upon movement in the opposite direction to release said locking meansior rendering the bushing fuse removable from said passageway, sealing means around said coacting terminal for simultaneously sealing one end of said passageway when the terminal is moved in the direction to efiect the locking action of said locking means, an end cap for said tube adapted to be blown free from said tube upon rupture of said fusible element by the expulsion action of said fuse device, and insulated means mounted adjacent said fusible element at said opposite end for maintaining electrical contact between said cap and said coaxial terminal so as to elongate and quickly extinguish the are formed upon rupture of the fusible element.

8. A renewable expulsion fuse device for electric apparatus of the type employing a liquid dielectric and including a high voltage bushing with a passageway for said fuse device in said bushing, comprising a fuse tube of insulating material, an axial terminal mounted partially within and at one end of said fuse tube, a coaxial terminal mounted outside of and closely adjacent the opposite end of said fuse tube, a fusible element located in said fuse tube closely adjacent said opposite end and electrically interconnecting said terminals, a resilient contact supported within said passageway so as to be electrically connected with one of said terminals when said fuse device is in said passageway, a coacting terminal engageable with said axial terminal, locking means in said passageway having resilient portions engageable with said coasting terminal upon movement thereof in one direction relative to the axial terminal for rendering said bushing fuse immovable in said passageway and upon movement in the opposite direction to release said locking means for rendering the bushing fuse removable from said passageway, sealing means around said coasting terminal for simultaneously sealing one end of said passageway when the terminal is moved in the direction to effect the locking action of said locking means, an end cap for said tube adapted to be blown free from said tube upon rupture of said fusible element by the expulsion action of said fuse device, and means mounted adjacent said fusible element at said opposite end and associated with the blowing oil of said cap for quickly elongating and extinguishing the are formed upon rupture of said fusible element.

GEO :c F. LINCKS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,458,948. January 11, 1949.

GEORGE F. LIN CKS It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 6, for tube 13 read tube 14; line 61, for element 30 read element 20;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 7th day of June, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommicsz'oner of Patents.

Certificate of Correction Patent No. 2,458,948. January 11, 1949.

GEORGE F. LIN CKS It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 6, for tube 13 read tube 14; line 61, for element 30 read element 20;

and that the said Letters Patent shouldbe read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 7th day of June, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

